Adjustment of relay contact-fingers.



C. O. HARRINGTON. ADJUSTMENT 'OF RELAY CONTACT FINGERS, APPLICATION FILED SEPT. 11. 1917.

WITNESSES Patented Jan. 22, 1918.

EINITED gTATES PATENT QFFICE,

CLINTON O. HARRINGTON, OF SWISSVALE, PENNSYLVANIA, ASSIGNOB TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION 01" PENNSYLVANIA.

ADJUSTMENT 0F RELAY GCNTACT-FINGERS.

Application filed September 11, 1917.

To all whom it may concern:

Be it known that I, CLINTON O. HARRING- TON, a citizen of the United States, residing at Swissvale, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Adjustment of Relay Contact-Fingers, of which the following is a specification.

lWIy invention relates to relay contacts, and particularly to the adjustment of one of the members of a contact so as to secure a predetermined amount of contact pressure between such member and the other member of the contact when the contact is fully closed.

- I will describe one method embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Figure 1 is a fragmentary view showing in side elevation a portion of a relay including a contact which may be adjusted in accordance with my invention. Fig. 2 is a fragmentar view showing in bottom plan the finger B shown in Fig. 1.

.Similar reference characters refer to similar parts in each of the views.

Referring first to Fig. 1, I have here shown a portion of a relay comprising an electromagnet M, a movable contact member F, and a fixed contact member or block K, the latter usually being formed of carbon. The electromagnet M comprises, as usual, a pair of windings W' (one only being shown, because one is directly behind the other in the drawing), a pole-piece P for each winding, and an armature A pivotally mounted in brackets 9 of non-magnetizable material attached to the pole-pieces. The pole-pieces are provided with the usual core pins 10 of non-magnetizable material to prevent the armature from sticking to the pole-pieces due to residual magnetism when the magnet windings are deenergized.

Attached to the armature A is a yoke Y of insulating material, which yoke carries the movable contact member F. As here shown, this contact member comprises a finger 11 of comparatively rigid electro-conductive material mounted on the yoke Y, a

spring 12 of comparatively flexible electro- I conductive material-attached at one end to Specification of Letters Patent.

Patented J an. 22, 1918.

Serial No. 190,750.

tached to thefree end of the spring 12 and arranged to engage with the fixed block K when the armature is in the attracted posiown.

The parts of the contact FK are, as usual, s0 proportioned that when the armature A is open, that is, against its back stop S due to the electromagnet being denergized, the contact tip 13 is out of engagement with contact block K, but that when the electromagnet is energized so that the armature is attracted the contact tip 13 reaches block K before the armature reaches the core pins 9, whereupon during the remainder of the movement this tip slidcs along on the block due to the flexibility of the spring 12. This flexibility of the spring 12 determines the pressure between tip 18 and block K when the armature is closed against the core pins. That is, if the spring is comparatively stifi', it will, of course, cause the tip to exert comparatively high pressure on the block, whereas if the spring is less stiff it will cause less pressure of the tip on the block. The

electrical resistance of the contact varies,

however, with variations in pressure, the resistance being low when the pressure is high, and higher when the pressure is lower, but as is well understood, this resistance must be a predetermined value in relays which are used for certain purposes, such as for the control of railway signals. It follows, then, that in order to insure that the contact resistance shall be the desired value, the pressure must be a certain value, which means that, all other things being equal, the spring 12 must have a certain degree of stiffness.

If all springs 12 could be'so selected that they have uniform stiffness, then each contact could be assembled so that the tip 13 would be deflected a certain amount, that is, would have slid a certain distance on block K, when the armature reaches the core pins; the contact pressure, and consequently the contact resistance, would then be the desired value. I have found. however, that the commercial stock available for the springs 12 varies in stiffness through a wide range, probably 13 257 this variation being due partly to inequalities in rolling and tempering, but principally to variations in the thickness of the material. The result is that if the amount of deflection of the tip-is depended upon for purposes of adjustment, the resistance of the contacts will vary through a wide range.

In my invention, I provide for varying the'length (Z of the contact spring in accordance with the stiffness. That is, the stifl'er the spring the greater should be the length d to cause the spring to exert the same pressure when the armature exerts a given pressure on the spring. One convenient way to provide for this adjustment is to temporarily clamp the spring 12 to the finger 11 so that the spring can he slid toward and away from the finger. A force 7' is then applied to the tip, which force is preferably equal to the desired contact pressure, and the deflection a of the tip is noted. If this deflection is greater than the proper value, the spring is shortened by sliding it toward the finger 11, whereas if the deflec tion is less than the desired value, the spring is lengthened by sliding it away from finger 11. When the given force causes the proper amountof deflection of the tip, the spring is riveted, or otherwise secured, to the finger 11 in its adjusted position. It is then known that when the armature is closed against its core pins and the tip 13 is deflected a given amount, the tip will exert the desired force against the block K, and that consequently deflection, and then permanently attaching the spring to the finger.

It will be seen from the foregoing that in agroup of contact members the tips 13 of the several members will be at different distances from the fingers 11, and that consequently unless some means for compensation be provided, when these members are mounted on armatures the tips 13 will be in different positions with respect to the armatures. Then if the fixed contact blocks K all bear the same relation to the pole-pieces P, the tips 13 would engage the different blocks K at various points .on the blocks, and with different pressures for the various contacts when the contacts are closed. To avoid these variations, any suitable compensating means may be provided. such for example as the means shown and described in an application filed by Clarence S Snavely washers 14 of plastic material, such as cement, between the finger 11 and .yoke In assembling, the spring 12 is first adjusted to the desired length as hereinbefore explained, and the finger 11 is then applied to the yoke while the washers 14E are plastic, the bolts 15 being put in place but not tightened. The finger 11 is then shifted longitudinally until'the tip 13 is the'proper distance from the armature A, this shifting being permitted by the elongated holes 16 in the finger. The bolts 15 are then drawn up until the tip 13 occupies the desired posi' tion with respect to the plane of the armature, whereupon the washers 14 are allowed to harden. It is clear,then, that-when the armature is mounted in the'relay, the tip 13 will occupy the proper position with re spect to the fixed block K, and will bear against this block with the proper pressure when the armature is closed against the core Although I have herein shown and described only one method of adjustment embodying my invention, it is understood that various changes and modificationsmay be made therein within the scope of the appended claims without vdeparting from the spirit and scope of my invention.

Having thus described my invention, what I claim is: j V

1. A method of adjusting-a relay contact member comprising a contact finger and a flexible contact spring, which consists in adjustably mounting the spring upon its finger, applying a predetermined force. to said spring at or near the free end thereof,

adjusting the spring with relation to the finger until the spring is deflected a predetermined .amount by said force, and then permanently securing the spring to the finger in the adjusted position.

2. A method of adjusting a relay contact,

member comprising a contact finger and a flexible contact spring, which consists .in a'djustably mounting the spring upon its finger, applying force to said spring at or adjacent to the free end thereof. adjusting the spring with relation to the finger until the desired relation is secured between the force applied and the deflection of the finger, and then permanently securing the spring to the finger in the adjusted position.

In testimony whereof I aflix my signature in presence of two witnesses.

CLINTON O. HARRINGTON.

lVitnesses:

A. Hem IAN WEGNER, E. P. CRUM.

Copies of this patent may be obtained for five cents each, by addressing tht Gemm ip sr l gl Washington, 1),. Q, 

